Background: Diabetes mellitus and its complications are important cause for morbidity and mortality throughout the World. The aim of this study is to find the correlation between serum magnesium and macrovascular complications of type 2 diabetes mellitus. Materials and methods: This is a cross sectional observational study which was conducted in St Martha’s Hospital, Department of General Medicine, Bangalore, Karnataka between August 1st 2018 to May 31st 2020with 192 patients. Type 2 diabetic patients with macrovascular complications and Type 2 diabetic patients without macrovascular complications were included in this study.The collected data was analyses by using SPSS software Results: Among 192 subjects, 31 (16.1) had CAD, 164(85.4) had PVD, 5(2.6%) had CVA. Of which 8(25.8%), 81(49.4%), 3(60.0%) had hypomagnesemia respectively with P value < 0.05 which was statistically significant. Conclusion: We concluded that that serum Mg level was significantly lower in diabetic patients and was strongly associated with all macrovascular complications. The prediction of the onset of complications at an early stage helps in improving mortality and morbidity and to prevent the end organ damage.